Hahaha I basically did same thing. When I was 16 I was extremely overweight weighing 230 at 5'5 and I did heavy amounts alcohol like I didn't give a fk. When I was motivated to join the army I took away Alcohol/Processed Foods/Fast Foods and started working out and now im at 152lbs and running is very casual for me now. I always run 9 miles 4 days a week for the fun of it.]

Its all about mindset I tell you. I couldnt even run 1/2 a mile without stopping, now I can run 3 miles in less then 20 minutes and over achieve what I thought I couldn't do.